The best example of the development of thermal pockets 

 was obtained from bathythermograms taken from the USS 

 BOARFISH. Observations made for 14 hours in one locality 

 well within the pack ice region show that a vertical series of 

 pockets can exist (fig. 44). For example, at station B26 a cold 

 tongue was observed at 1 feet, below which a warm pocket 

 occurred. Still deeper a cold tongue was found overlying the 

 continuous warm layer just above the main thermocline. The 

 temperature range in these thermal pockets was found to vary 

 as much as 4 degrees F. 



Thermal pockets are undoubtedly due to the melting of ice 

 cakes coupled with the advection of warm, higher-salinity 

 water through the Bering Strait. This warmer water, being 

 of higher salinity, sinks below the colder but lower -salinity 

 melt water. The size and depth of the pocket is determined 

 by the size of the ice cake, the rate of mixing, the rate of 

 advection, the rate of melting, and the salinity of the water 

 masses. The salinity of the ice is lower than the salinity 

 of the surrounding water. The lower-temperature melt water 

 of low salinity may be less dense than warmer high-salinity 

 water and so may remain on top of the warmer layers without 

 producing instability. 



B21 B22 B23 B24 



B27 B28 



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1800 TIME (GCT) 



Figure 44. Fluctuations in vertical temperature structure (degrees F ) from repeated bathythermograph 

 observations for 13 hours on 6 August 1947 in the ice pack region (72° 02' N, 164° 50' W). 



